Compositions based on semicrystalline thermoplastic resins and block copolymers, resulting materials and methods for obtaining same

ABSTRACT

These compositions based on semi-crystalline thermoplastic resin and on ABC block copolymers result in materials or in items which exhibit an impact strength, an elongation at break, a resistance to cracking and to deformation under stress, and a thermal behavior which are improved with respect to semi-crystalline resin or resins alone or mixed with conventional impact additives, while retaining a high modulus and thus a degree of stiffness. They are generally suitable for the preparation of items or articles, such as sheets, films, pipe sheathings, tubings, pipes, yarns, strands, cable sheathings, bracing wires, leaktight sheathings, sleeve tubes, both mono- and multilayer, shaped components, molded panels, thermoformed articles, sections, bottles or powders for coating substrates. The materials or items obtained from these compositions exhibit a characteristic morphology visible in electron microscopy.

This application claims benefit, under U.S.C. § 119 or §365 of FrenchApplication Number 97/15389, filed Dec. 7, 1997, and PCT/FR98/02635flied Dec. 7, 1998.

The present invention relates to compositions based on semi-crystallinethermoplastic polymers, to materials obtained from these compositionsand to their processes of preparation. Thermoplastic resins, which areeasy to process and convert, are widely used in many fields according totheir specific mechanical and chemical properties.

Mention may in particular be made, among semi-crystalline thermoplasticresins, of polyamides (PA), polyolefins, fluorinated resins, vinylresins, polyesters, polycarbonates, polyoxyalkylenes, polyurethanes orpolysiloxanes.

However, as their mechanical, chemical and/or thermal properties are notalways sufficient, in particular their impact strength at roomtemperature and/or at low temperature, as well as their elongation atbreak, there is often reason to add specific additives to them.

In order to improve certain properties, in particular the impactstrength, it is possible to add plasticizers which lower theintermolecular interaction forces and bring about a decrease in themodulus and thus a softening of the polymer to which they are added,which is not necessarily desired in certain applications. Furthermore,these substances exhibit the well-known disadvantage of exuding more orless rapidly from the polymer material in which they are incorporated,which is thus reflected by a decrease in the impact strength and issometimes accompanied by a shrinkage of the material.

Provision has also been made to add elastomers and/or thermoplasticelastomers (TPE) as impact additives, as disclosed in EP 239,707. Thecompositions thus obtained exhibit an improved impact strength withrespect to the thermoplastic resin alone but it is necessary toincorporate a large amount of elastomers or of TPE in the composition inorder to obtain a significant improvement in these properties, typicallyof the order of 20% by weight of the total mass of the composition, andthis is harmful to the intrinsic properties of the semi-crystallinethermoplastic resin.

It is known in the prior art that, when conventional impact or otheradditives are added to a semi-crystalline thermoplastic resin, thedomains composed of these additives have a tendency to come together inthe resin. This phenomenon, which is harmful to the properties of thefinal material obtained by shaping the composition, is known ascoalescence.

Another known technical solution consists in combining, by the blendroute, another polymer with the thermoplastic resin, the properties ofwhich it is desired to improve. However, it is often difficult to mixpolymers of different chemical natures, given the incompatibility whichcan exist between the resins which it is desired to combine; thisincompatibility is reflected by a macroseparation of phases which canresult, if it is not controlled, in materials of coarse morphology andthus with poor mechanical properties. To overcome this problem, aso-called compatibilizing agent is added, which agent is confined to theinterface between the incompatible polymers and has the role of reducingthe size of the separate phases to a few micrometers by limiting thecoalescence. The addition of these compatibilizing agents (or their insitu synthesis) has the effect, on the one hand, of reducing the size ofthe domains constituted by the second polymer dispersed in the matrixcomposed of the first polymer and, on the other hand, of improving thecohesion between these domains and the matrix. Compatibilizing agents(block copolymer(s)) for incompatible resins are disclosed, for example,in DE 4,416,853 and DE 4,416,855. However, for many applications, thisroute does not make it possible to obtain materials having the requiredmechanical and chemical resistance properties.

U.S. Pat. No. 5,484,838 discloses a mixture of at least two polymerschosen from a collection of polymers. The styrene-butadiene blockcopolymer and the methyl methacrylate-styrene-butadiene block copolymerare indicated among these polymers. For a person skilled in the art, thefirst copolymer is recognized as a diblock where each of the blocksappears separated by a single hyphen. Likewise, for the same reason, thesecond block copolymer is recognized as being a diblock where each ofthe blocks appears separated by a single hyphen and is composed of ablock formed of methyl methacrylate and styrene monomers and of apolybutadiene block.

Patent Application JP-A-63-308055 discloses a composition based onpoly(vinylidene difluoride) (PVDF) comprising a block copolymer of A-Bdiblock, A-B-A triblock or A-B starbranched type, according to thenumber of dithiocarbonate groups of the radical initiator used in thesynthesis of the copolymer.

The monomer or monomers used to synthesize the block A compatible withPVDF are chosen from methyl methacrylate, methyl acrylate and vinylacetate.

The block B preferably has a glass transition temperature Tg notexceeding 0° C. and better still not exceeding −10° C.

On the basis of these Tg values, the monomer intended to constitute theblock B is chosen on the basis of the known Tg values of homopolymerswith a molecular weight of at least 10,000 obtained by conventionalradical polymerization. Thus, ethyl acrylate results in such ahomopolymer with Tg=−24° C. The list provided contains: butyl acrylate(−54° C.), 2-ethylhexyl acrylate (−85° C.), hydroxyethyl acrylate (−15°C.) and 2-ethylhexyl methacrylate (−10° C.).

The block B can also be composed of several monomers chosen as afunction of the Tg of their corresponding homopolymer and in proportionswhich can be calculated so as to obtain, for the block B copolymer, a Tgnot greater than 0° C.

The block copolymer comprises from 5 to 75% by weight of block A withrespect to the total weight and the composition preferably comprisesfrom 5 to 30 parts of the block copolymer per 100 parts by weight ofPVDF.

This composition based on PVDF (Kynar 740®) is disclosed as havingimproved properties with respect to those of PVDF alone, in particularas regards the flexibility, the impact strength, the stress at break andthe elongation at break.

However, this composition of the prior art exhibits disadvantages. Firstof all, the dithiocarbonate radical initiator comprises sulphur and thesaid composition has a tendency to turn yellow. Furthermore, Examples 1to 5 show that, in the synthesis of the block copolymers, formation ofhomopolymer(s) takes place to contents of 13 to 18%. These homopolymerscan be extracted from the diblock with acetone. Finally, when the blockB is incompatible with the PVDF, as it is elastomeric in nature, itconstitutes discontinuous soft domains. These soft domains have theeffect of rendering the composition softer than PVDF alone. In otherwords, the limiting or maximum temperature of use of the composition,characterized by the Vicat temperature, is reduced and this constitutesa significant disadvantage.

Patent JP-B-46-7457 discloses a composition based on poly(vinylchloride) (PVC) comprising a block copolymer of A-B diblock type.

The A-B diblock is obtained by living anionic polymerization of the Bblock and then of the A block.

The monomer used to synthesize the elastomeric B block is a diene chosenfrom butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene or2-phenyl-1,3-butadiene.

The monomer used to synthesize the A block from the living B polymer ismethyl methacrylate (MMA).

The A-B diblock copolymer is thus poly(MMA)-poly(diene) and comprisesfrom 20 to 80% by weight of poly(MMA) and from 80 to 20% by weight ofpoly(diene).

It is indicated that the poly(MMA)-poly(diene) diblock copolymercomprises a small amount of polydiene homopolymer and that it ispossible to remove this homopolymer by extraction with a solvent, suchas petroleum ether or cyclohexane.

The material obtained from the PVC composition comprising thispoly(MMA)-poly(diene) diblock is disclosed as having better propertiesthan a material obtained from a PVC composition mixed with an elastomerconsisting of a statistical copolymer.

The impact strength, the stress at break and the transparency areselectively increased. On the other hand, the hardness (Rockwell R) ofthe various materials in Table 1 is lower than that of unmodifed PVC andthe higher the content of diblock copolymer, the more the hardness ofthe material decreases.

Table 1 also shows a decrease in transparency and an increase in thehaze with the increase in the content of diblock copolymer.

This situation is a hindrance to the uses of the material obtained fromthe PVC+poly(MMA)-poly(diene) mixture because the aim is to improve theimpact strength without decreasing the hardness or without reducing thetemperature range of use of the material. This temperature range ischaracterized by the Vicat temperature or Vicat point.

The first aim of the present invention is to provide compositionscomprising:

-   -   a semi-crystalline thermoplastic resin X₁ or several compatible        thermoplastic resins X₁ to X_(n), at least one X₁ of which is        semi-crystalline, and    -   at least one block (sequential) copolymer,    -   n being an integer equal to or greater than 1,

resulting; by shaping, in materials or in items having good hardness andexhibiting an impact strength, an elongation at break, a resistance tocracking, a resistance to deformation under stress and a thermalbehaviour (temperature range of use) which are improved with respect tothe semi-crystalline resin or resins, alone or mixed with knownadditives, of the prior art.

The above problem arises in particular with halogenated thermoplasticpolymers or copolymers, in particular PVDF, PVC or chlorinated PVC(CPVC).

Furthermore, the Applicant Company has found that PVDF- or PVC-basedcompositions reported above comprising blocks of A-B or A-B-A diblock,or A-B starbranched type exhibit a major disadvantage since theycomprise homopolymers of A or B type as by-products of the synthesis ofthese blocks: the presence of the homopolymers is particularly harmfulto the mechanical properties of the material, in particular as regardstheir hardness at the Vicat point and especially their tensilebehaviour.

The abovementioned documents have possibly provided for a purificationof the block copolymers at the end of their synthesis by selectiveextraction using solvent (acetone, petroleum ether or cyclohexane) Thisextraction is a purification stage which is both expensive and tediousand which is particularly disadvantageous to operate industrially, fromthe teachings of the above two Japanese documents.

Thus, a second aim of the present invention is to find a technicalsolution to the problem set out above which does not require selectiveextraction by solvents and which consequently greatly simplifies theindustrial feasibility.

The first aim is achieved by a composition intended to be formed into amaterial or an item which comprises:

-   -   a semi-crystalline thermoplastic resin X₁ or several compatible        thermoplastic resins X₁ to X_(n), at least one X₁ of which is        semi-crystalline, and    -   at least one block (sequential) copolymer,    -   n being an integer equal to or greater than 1,        characterized in that:

the block copolymer comprises at least three blocks A, B and C connectedto one another in this order, each block being either a homopolymer or acopolymer obtained from two or more monomers, the A block beingconnected to the B block and the B block to the C block by means of acovalent bond or of an intermediate molecule connected to one of theseblocks via a covalent bond and to the other block via another covalentbond, and in that:

-   -   the A block is compatible with the thermoplastic resin or resins        X₁ to X_(n),    -   the B block is incompatible with the thermoplastic resin or        resins X₁ to X_(n) and incompatible with the A block,    -   the C block is incompatible with the thermoplastic resin or        resins X₁ to X_(n), the A block and the B block.

The B block generally has a glass transition temperature Tg_((B)) ofless than 23° C.

The Tg_((B)) of the B block is advantageously less than 0° C.

The Tg_((B)) of the B block is preferably less than −50° C.

The choice of the temperature Tg_((B)) depends on the temperature Tawhich can be adopted by the material or item obtained from thecomposition according to the invention during use. This is because, atthis temperature Ta, it is preferable for the B block to be elastomericand not in the vitreous state.

The C block preferably has a glass transition temperature Tg_((C)) or amelting temperature M.t._((C)) which is greater than the Tg_((B)) of theB block.

This characteristic confers the possibility of the C block being in thevitreous state or in a partially crystalline state and the B block inthe elastomeric state, for the same temperature of use Ta.

According to the present invention, it is possible to choose the natureof the B blocks in order to have a certain specific Tg_((B)) and thus,at the temperature of use. Ta of the material or of the item formed fromthe composition, to have an elastomeric or flexible state of these Bblock polymers. On the other hand, it being possible for the C blockpolymers to have a Tg_((C)) or an M.t. which is greater than theTg_((B)), they can be in a relatively stiff vitreous state at the sametemperature of use.

As the C blocks are incompatible with the thermoplastic resin or resins,the A blocks and the B blocks, they form a rigid discontinuous phasewithin the material, forming nanodomains included in the material whichact as anchorages in the domain of one of the ends of each B block. Theother end of each B block is connected to an A block which has a highaffinity with the semi-crystalline thermoplastic resin or resins. Thishigh affinity provides a second anchorage in the domain of the secondend of the B block.

The compatibility of the A blocks and the incompatibilities stated aboveof the B and C blocks, with the choice of the Tg_((B)) and of theTg_((C)) or of the M.t._((C)) of the composition according to theinvention, allow a greater effectiveness of the elastomeric or soft Bblocks on the impact strength properties of the material, while allowingthe hardness of the material to be retained or even improved. The Vicattemperature of the material formed from the composition is found to beretained or increased with respect to the material formed from thesemi-crystalline thermoplastic resin or else from the mixture ofsemi-crystalline thermoplastic resins.

The A block of an ABC copolymer is regarded as compatible with thesemi-crystalline thermoplastic resin if the A polymer identical to thisblock (thus without B and C sequences) is compatible with this resin inthe molten state. Likewise, the A and B blocks are regarded ascompatible if the A and B polymers identical to these blocks arecompatible. Generally, compatibility between two polymers is understoodto mean the ability of one to dissolve in the other in the molten stateor else their complete miscibility.

In the contrary case, the polymers or blocks are said to beincompatible.

The lower the enthalpy of mixing of two polymers, the greater theircompatibility. In certain cases, there is a specific favourableinteraction between the monomers which is reflected by a negativeenthalpy of mixing for the corresponding polymers. In the context of thepresent invention, it is preferred to employ compatible polymers forwhich the enthalpy of mixing is negative or zero.

However, the enthalpy of mixing cannot be conventionally measured forall polymers and thus the compatibility can only, be determinedindirectly, for example by torsional or oscillatory viscoelasticanalysis measurements or by differential calorimetric analysis.

For compatible polymers, 2 Tg values can be detected for the mixture: atleast one of the two Tg values is different from the Tg values of thepure compounds and lies within the range of temperatures between the twoTg values of the pure compounds. The mixture of two completely misciblepolymers exhibits a single Tg.

other experimental methods can be used to demonstrate the compatibilityof polymers, such as haze measurements, light scattering measurements orinfrared measurements (L. A. Utracki, Polymer Alloys and Blends, pp.64–117).

Miscible or compatible polymers are listed in the literature, see, forexample, J. Brandrup and E. H. Immergut: Polymer Handbook, 3rd Edition,Wiley & Sons 1979, New York 1989, pp. VI/348 to VI/364; O. Olabisi, L.M. Robeson and M. T. Shaw: Polymer Miscibility, Academic Press, New York1979, pp. 215–276; L. A. Utracki: Polymer Alloys and Blends, HanserVerlag, Munich, 1989. The lists which appear in these references aregiven by way of illustration and are not, of course, exhaustive.

In the same way as for the diblocks of the prior art, the synthesis ofthe triblocks results in mixtures because they comprise small amounts ofdiblocks and of monoblocks (homopolymers). The Applicant Company hasfound, surprisingly, that, in the case of the triblocks, these sideproducts were not harmful to the mechanical properties of thecomposition according to the present invention, unlike the compositionsof the prior art based on diblock and on PVDF or on PVC. For the latterknown compositions, the presence of these homopolymers is particularlyharmful to the properties of the material and therefore necessarilyrequires an expensive purification.

Thus, the composition according to the invention comprising a copolymerwith at least three A, B and C blocks can comprise, as side products ofits synthesis, a B-C diblock copolymer and optionally C homopolymer.

Likewise, the composition according to the invention comprising acopolymer with at least three A, B and C blocks can comprise, as sideproducts of its synthesis, an A-B diblock copolymer and optionally Ahomopolymer.

This is because the synthesis of a copolymer with at least three A, Band C blocks is preferably carried out by successively joining the Ablock to the B block and then to the C block or, conversely, the C blockto the B block and then to the A block, depending on the nature of thethree A, B and C blocks, the A block being, by definition, that which iscompatible with the compatible thermoplastic resin or resins X₁ toX_(n).

The B block is advantageously chosen from poly(dienes), in particularpoly(butadiene), poly(isoprene) and their statistical copolymers, oralternatively from poly(dienes), in particular poly(butadiene),poly(isoprene) and their statistical copolymers which are partially orcompletely hydrogenated.

The block copolymer comprising at least three A, B and C blocks is suchthat the A block is connected to the B block and the B block to the Cblock by means of one or more simple covalent bonds. In the case ofseveral covalent bonds between the A block and the B block and/orbetween the B block and the C block, it is possible to have there asingle unit or a linkage of units serving to join the blocks to oneanother. In the case of a single unit, the latter can originate from amonomer, known as a moderator, used in the synthesis of the triblock. Inthe case of a linkage of units, this linkage can be an oligomerresulting from a linkage of monomer units of at least two differentmonomers in an alternating or statistical order. Such an oligomer canconnect the A block to the B block and the same oligomer or a differentoligomer can connect the B block to the C block.

The composition according to the invention is advantageouslycharacterized in that it comprises:

-   -   from 25 to 95%, advantageously from at least 50% and preferably        from 65 to 95% by weight of the thermoplastic resin or resins X₁        to X_(n),    -   the remainder (to 100%) by weight of the copolymer comprising        the three A, B and C blocks connected to one another, these        percentages being calculated with respect to the total weight of        thermoplastic resin(s) with the block copolymer, and in that the        block copolymer comprises:    -   20 to 93 parts by weight of A sequences    -   5 to 68 parts by weight of B sequences    -   2 to 65 parts by weight of C sequences.

When the above composition comprises several block copolymers, eachcomprising the three A, B and C blocks, the amounts indicated above asparts by weight correspond to the sum of all the sequences of A, B and Ctype respectively.

A great many compositions can advantageously be obtained according tothe present invention. A non-exhaustive list is indicated below:

a) a composition which comprises, by weight:

-   -   at least 50% and preferably from 65 to 95% of poly(carbonate),        and    -   the remainder to 100% of the PMMA-PB-PS triblock copolymer,

these percentages being calculated with respect to the total weight ofthermoplastic resin(s) and of the block copolymer.

b) a composition which comprises, by weight:

-   -   at least 50% and preferably from 65 to 95% of poly(carbonate)        PC, and    -   the remainder to 100% of the poly(cyclohexyl methacrylate)-PB-PS        triblock copolymer,

these percentages being calculated with respect to the total weight ofthermoplastic resin(s) and of the block copolymer.

c) a composition which comprises, by weight:

-   -   at least 50% and preferably from 65 to 95% of poly(butylene        terephthalate) PBT, and    -   the remainder to 100% of the PMMA-PB-PS triblock copolymer,

these percentages being calculated with respect to the total weight ofthermoplastic resin(s) and of the block copolymer.

d) a composition which comprises, by weight:

-   -   at least 50% and preferably from 65 to 95% of poly(oxyethylene)        POE, and    -   the remainder to 100% of the PMMA-PB-PS triblock copolymer,

these percentages being calculated with respect to the total weight ofthermoplastic resin(s) and of the block copolymer.

e) a composition which comprises, by weight:

-   -   at least 50% and preferably from 65 to 95% of poly(propylene)        PP, and    -   the remainder to 100% of the poly(nonyl methacrylate)-PB-PS        triblock copolymer,

these percentages being calculated with respect to the total weight ofthermoplastic resin(s) and of the block copolymer.

f) a composition which comprises, by weight:

-   -   at least 50% and preferably from 65 to 95% of poly(amide) PA,    -   the remainder to 100% of the poly(caprolactone)-PB-PS triblock        copolymer,

these percentages being calculated with respect to the total weight ofthermoplastic resin(s) and of the block copolymer.

In the case of a fluorinated resin or of several compatible fluorinatedresins, preferably, the composition according to the invention ischaracterized in that it comprises, by weight, at least 50% andpreferably from 65 to 95% of semi-crystalline thermoplastic fluorinatedresin(s) and the remainder (to 100%) by weight of at least one blockcopolymer with a number-average molecular mass (M_(n)) of greater thanor equal to 20,000 g.mol⁻¹, preferably of between 50,000 and 200,000g.mol⁻¹, composed of:

-   -   20 to 93 and advantageously of 30 to 60 parts by weight of A        sequences,    -   5 to 50 and advantageously of 10 to 40 parts by weight of B        sequences,    -   2 to 50 and advantageously of 5 to 40 parts by weight of C        sequences,        the percentages being calculated with respect to the total        weight of fluorinated resin(s) with the block copolymer.

The composition preferably comprises poly(vinylidene difluoride) (PVDF)as thermoplastic fluorinated resin and a poly(methylmethacrylate)-poly(butadiene)-poly(styrene) PMMA-PB-PS triblockcopolymer.

The compositions according to the invention comprising at least 50% andpreferably from 65 to 95% of semi-crystalline thermoplastic fluorinatedresin(s) exhibit an impact strength, an elongation at break and anincrease in the yield point (resistance to deformation under stress,absence of necking and of whitening during traction) which are improved,while retaining a high modulus and thus a degree of rigidity, andexhibit a semi-crystalline nature.

These compositions can be used for the preparation of materialssubjected to stresses under high- and/or low-temperature conditions, incontact with particularly aggressive substances (such as hydrocarbons,strong acids, solvents, inorganic and organic bases), during which theirproperties of resilience are particularly required. The preferredcompositions are those which comprise at least 10% of ABC triblockcopolymer(s) (with respect to the fluorinated resin(s)+ABC triblock(s)total mass).

The compositions according to the invention as defined above based onfluorinated resin are particularly suited to the manufacture ofleaktight sheathings for flexible metal pipes for the extraction and/ortransportation of gas and hydrocarbons in the oil and gas industries.These leaktight sheathings are generally provided in the form ofsingle-layer or multi-layer pipes manufactured by extrusion orcoextrusion, into which the flexible metal pipe is subsequentlyinserted, or else formed directly on the flexible pipe.

In the case of a vinyl resin or of several compatible vinyl resins,preferably, the composition according to the invention is characterizedin that it comprises, by weight, at least 50% and preferably from 65 to95% of semi-crystalline thermoplastic vinyl resin(s) and the remainder(to 100%) by weight of at least one block copolymer with an M_(n) ofgreater than or equal to 20,000 g.mol⁻¹, preferably of between 50,000and 200,000 g.mol⁻¹, composed of:

-   -   20 to 93 and advantageously of 30 to 60 parts by weight of A        sequences,    -   5 to 68 and advantageously of 11 to 55 parts by weight of B        sequences,    -   2 to 50 and advantageously of 5 to 49 parts by weight of C        sequences,        the percentages being calculated with respect to the total        weight of vinyl resin(s) with the block copolymer.

The composition preferably comprises poly(vinyl chloride) (PVC) assemi-crystalline thermoplastic vinyl resin and a poly(methylmethacrylate)-poly(butadiene) poly(styrene) triblock copolymer.

The composition advantageously comprises chlorinated poly(vinylchloride) (CPVC) as semi-crystalline thermoplastic vinyl resin and apoly(methyl methacrylate)-poly(butadiene)-poly(styrene) triblockcopolymer.

The compositions comprising at least 50% by weight of semi-crystallinethermoplastic vinyl resin(s), preferably from 60 to 95%, exhibit animpact strength and a Vicat temperature which are improved with respectto PVC resins alone or mixed with conventional impact additives.

These vinyl compositions can, for example, be used for the preparationof window or pipe sections, switch cases and boxes, films, panels orbottles of mono- and multilayer type.

In the case of a styrene resin or of several compatible styrene resins,preferably, the composition according to the invention is characterizedin that it comprises, by weight, at least 50% and preferably from 65 to95% of semi-crystalline styrene thermoplastic resin(s) and the remainder(to 100%) by weight of at least one block copolymer with an M_(n) ofgreater than or equal to 20,000 g.mol⁻¹, preferably of between 50,000and 200,000 g.mol⁻¹, composed of:

-   -   20 to 93 and advantageously of 30 to 60 parts by weight of A        sequences,    -   5 to 50 and advantageously of 10 to 40 parts by weight of B        sequences,    -   2 to 50 and advantageously of 5 to 49 parts by weight of C        sequences,        the percentages being calculated with respect to the total        weight of styrene resin(s) with the block copolymer.

The composition preferably comprises poly(styrene) as semi-crystallinethermoplastic styrene resin and apoly(styrene)-poly(butadiene)-poly(methyl methacrylate) triblockcopolymer.

The semi-crystalline thermoplastic styrene resin is generallysyndiotactic.

The composition according to the invention can also comprise one or morethermoplastic polymer(s) D compatible with the C sequences, D beingpresent in an amount of less than 10% of the total mass of thermoplasticresin(s) X₁ to X_(n) and of the block copolymer(s) with, possibly, itsside products.

The D polymers can be either homopolymers or statistical copolymers.Mention may be made as D polymer, for triblocks having C sequencesderiving from styrene, of poly(phenylene ether), poly(vinyl ether) andpoly(methylphenylsiloxane).

A process for the preparation of a material or of an item from thecomposition according to the invention is advantageously characterizedin that it comprises the following stages:

-   -   the thermoplastic resin(s) X₁ to X_(n) is (are) mixed in the        molten state with the block copolymer(s) and optionally the        thermoplastic polymer(s) D, optionally in the presence of        additives and/or of fillers which can remain in a solid state,    -   the liquid or the molten material (optionally with the suspended        fillers) thus obtained is cooled to give a material or an item        in the solid state.

This process, which consists in mixing the molten resin(s) with themolten copolymer(s), is distinguished by its simplicity ofimplementation. It results, by cooling, in a material having acharacteristic structure.

The compositions according to the invention result in materials or itemsgenerally exhibiting an extremely fine and regular specific morphologywhich can be obtained by the process comprising a simple mixing in themolten state of the constituents and does not require severe mixing ordispersing techniques. Furthermore, this morphology is retained in theitems formed, in particular by injection or extrusion of the material(for example as granules), which are subjected to a new cycle ofmelting, followed by cooling.

The material or item having a composition according to the invention canbe characterized by the following specific heterogeneous structure:

-   -   the structure is formed of a continuous phase (matrix) formed        essentially of the thermoplastic resin or resins X₁ to X_(n)        comprising a discontinuous phase dispersed in a very even manner        as nodules with a size D_(n) of less than 0.5 micrometer,    -   each nodule comprises an internal region composed mainly or        essentially of C blocks and an external peripheral region        comprising the B blocks of the copolymers with at least three A,        B and C blocks connected to one another in this order, this        peripheral region surrounding the internal region in a        continuous or discontinuous fashion.

The industrial implementation of the compositions advantageously makesuse of the triblocks with their side products of their synthesis. Inthis case, the morphology changes slightly and a material or item isobtained which is characterized in that the copolymer with at leastthree A, B and C blocks comprises, as side products of its synthesis, aB-C diblock copolymer and optionally C homopolymer and that theheterogeneous structure specific to this composition is modified in thatthe internal region of the nodules, composed mainly or essentially of Cblocks, surrounds one or more domains composed essentially of B blocksof the B-C diblock.

The relative proportions by mass of semi-crystalline thermoplasticresins and of triblocks are advantageously chosen so that the noduleshave a size D_(n) ranging from 30 to 350 nanometers.

The choice is preferably made in order for the nodules to have a sizeD_(n) ranging from 60 to 250 nanometers.

Generally, the material or item is also characterized in that thedistance between two neighbouring nodules D_(i) is between 1.1 and 5times the value of the size D_(n). It is found that this distance D_(i)is substantially constant and this indicates a very homogeneousdistribution of the nodules in the material.

This very homogeneous distribution is one of the major advantages of theinvention because it is possible to introduce the block copolymer asdefined in claim 1 to a very high level by weight, without observingcoalescence harmful to the properties of the material or of the item.

Mention may in particular be made, among semi-crystalline thermoplasticresins, of

-   -   fluorinated resins known for their good thermal behaviour, their        chemical resistance, in particular to solvents, resistance to        bad weather and to radiation (UV, and the like), their        impermeability to gases and to liquids, and their electrical        insulating property.

Mention will very particularly be made of vinylidene fluoride (VF2)homo- and copolymers preferably-comprising at least 50% by weight of VF2and at least one other fluorinated monomer, such aschlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP),trifluoroethylene (VF3) or tetrafluoroethylene (TFE),

-   -   trifluoroethylene (VF3) homo- and copolymers,    -   copolymers, in particular terpolymers, combining the residues of        chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE),        hexafluoropropylene (HFP) and/or ethylene units and optionally        of VF2 and/or VF3 units.    -   polyamide or PA resins which comprise aliphatic and/or        cycloaliphatic and/or aromatic units.

Mention may be made of the resins obtained by polycondensation of one ormore lactams or of α, ω-amino acids or by a substantially stoichiometricpolycondensation of one or more aliphatic diamine(s) and of one or morealiphatic dicarboxylic acid(s).

The preferred lactams are caprolactam, decalactam, undecalactam anddodecalactam.

The preferred α,ω-amino acids are 6-aminohexanoic acid, 10-aminodecanoicacid, 11-aminoundecanoic acid and 12-aminododecanoic acid. Thecarbon-comprising chain of the aliphatic α,ω-diamines can be linear(polymethylenediamine) or branched and preferably comprises up to 12carbon atoms. Preferred diamines are hexamethylenediamine (HMDA) anddodecamethylenediamine.

The carbon-comprising chain of the aliphatic α,ω-dicarboxylic acids canbe linear or branched. The preferred diacids are adipic acid, azelaicacid, sebacic acid and 1,12-dodecanedoic acid.

Mention may be made, by way of illustration of such PA resins, of:

-   -   polyhexamethyleneadipamide (PA-6, 6),    -   polyhexamethylenesebacamide (PA-6, 10),    -   polyhexamethylenedodecanediamide (PA-6, 12),    -   poly(undecanoamide) (PA-11),    -   polylauryllactam (PA-12),    -   polydodecamethylenedodecanediamide (PA-12, 12),    -   the copolymers of the above.

The PAs have a number-average molecular mass M_(n) generally greaterthan or equal to 5000 g.mol⁻¹. Their inherent viscosity (measured at 20°C. for a 0.5 g sample in 100 g of meta-cresol) is generally greater than0.7.

-   -   polyolefins and in particular polyethylene (PE), polypropylene        (PP), polyisoprenes, poly-1-butene or copolymers of olefins,        such as PP/PE or PP/polyisoprene;    -   vinyl resins having a certain degree of crystallinity and in        particular poly(vinyl chloride) (PVC) with syndiotactic        segments, chlorinated PVC (CPVC) and vinylidene chloride (PVDC),        or syndiotactic PS, which are optionally copolymerized;    -   polyesters and in particular poly(ethylene terephthalate) (PET)        or poly(butylene terephthalate) (PBT);    -   polycarbonates (PC), among which may be mentioned        poly(oxycarbonyloxy-1,4-phenyleneisopropylidene-1,4-phenylene),        poly(oxycarbonyloxy-1,4-phenylene-methylene-1,4-phenylene) or        poly(oxycarbonyloxy-1,4-phenylenethio-1,4-phenylene);    -   polyoxyalkylenes and in particular polyoxymethylenes (POM),        polyoxyethylenes (POE) and polyoxypropylenes (POP);    -   aliphatic polyketones and in particular alternating        (ethylene-ketone) copolymers and terpolymers        (ethylene-ketone-propylene).

Mention will very particularly be made, by way of example of A sequenceswhich are compatible with VF2 homo- and copolymers, PVC, CPVC, POE andPCs, of those which are derived from alkyl(alkyl)acrylate, for examplefrom methyl methacrylate (MAM) and/or from methyl acrylate, and/or thosederiving from vinyl acetate. PMMA sequences, preferably syndiotacticPMMA sequences, are advantageously preferred. Mention may also be madeof statistical copolymers of butadiene and of acrylonitrile comprisingfrom 23 to 45% of acrylonitrile, statistical copolymers of ethylene andof vinyl acetate comprising from 65 to 75% of vinyl acetate andstatistical copolymers of styrene and of acrylonitrile comprising 28% ofacrylonitrile which are compatible with PVC.

Mention will very particularly be made, by way of example of A sequenceswhich are compatible with PA resins, of those which are derived fromcaprolactone and/or from glycidyl methacrylate and/or from (meth)acrylicacid. Mention may also be made of statistical copolymers of p-(2hydroxyhexafluoroisopropyl)styrene and of styrene which are compatiblewith PA-6 and PA-12.

Mention will be made, by way of example of A sequences which arecompatible with polypropylene, of those which are derived from nonylmethacrylate.

Mention will be made, by way of example of A sequences which arecompatible with polyesters and polyoxymethylenes, of those which arederived from alkyl(meth)acrylate(s).

Mention will be made, by way of example of A sequences which arecompatible with polycarbonates, of those which are derived from methylmethacrylate.

Mention may be made, among the B sequences, of polymers obtained fromalkyl acrylates, such as, for example, butyl acrylate or 2-ethylhexylacrylate and preferably dienes, such as butadiene or isoprene, which areoptionally partially or completely hydrogenated, and particularlyadvantageously those with the lowest Tg, for example poly(1,4-butadiene)with a Tg (approximately −90° C.) which is less than that ofpoly(1,2-butadiene) (approximately 0° C.).

Mention may be made, among the C blocks or sequences of the ABC triblockcopolymers, of the sequences which are derived from vinylaromaticcompounds, such as styrene, α-methylstyrene or vinyltoluene, and thosewhich are derived from alkyl esters of acrylic acid and/or methacrylicacid having from 1 to 18 carbon atoms in the alkyl chain.

The triblocks which comprise sequences deriving fromalkyl(alkyl)acrylate can be prepared in particular by anionicpolymerization, for example according to the processes disclosed inPatent Applications EP 524,054 and EP 749,987.

The compositions according to the invention can also comprise variousmacromolecular or otherwise, organic or inorganic, additives and/orfillers and/or dyes and/or pigments well known in the literature.

Mention may be made, by way of non-limiting examples of fillers whichare insoluble in these compositions, of mica, alumina, talc, titaniumdioxide, carbon black, glass fibres, carbon fibres or fibres ofmacromolecular compounds.

Mention may be made, by way of non-limiting examples of additives, ofanti-U.V. agents, flame-retardent agents, conversion agents orprocessing aids.

The sum of these various additives and fillers generally represents lessthan 20% of the thermoplastic resin(s)+triblock(s) total mass.

By way of example, in the multi-layer leaktight sheathings disclosed inU.S. Pat. No. 5,601,893, the polymer can advantageously be replaced by afluorinated composition according to the present invention.

These compositions are also well suited to the preparation of chemicalengineering components, in particular in the form of tubes or pipes, andto the preparation of items in the field of the building and publicworks industries, such as cable sheathings or bracing wires, and ofmono- or multilayer films and sheets for any type of industry. Thecompositions can be subjected to shaping by extrusion blow-moulding inorder to result in films.

Mention will be made, by way of example of sheathings, yarns, strands,cables and bracing wires, of those disclosed in Patent Applications EP671,502 and EP 671,746, where the polymer can be replaced by acomposition according to the present invention.

As the fluorinated compositions exhibit properties of resistance todeformation under stress and in particular a decrease of, indeed in somecases the suppression of, the fall in modulus beyond the yield point,this allows them to be used in the preparation of articles and ofmaterials requiring a deformation under stress during their positioning;this is typically the case in the renovation of conduits in distributionnetworks for natural gas, where plastic pipes are jacketed and can thusbe inserted into existing conduits, which are generally metallic.

The compositions according to the invention based on PA resin canadvantageously be used in the preparation of articles for theautomobile, building, sports and leisure industries (pipework, pipes,bumpers, body parts, engineering parts, moulded panels, thermoformedarticles, powders for the coating of substrates, and the like).

In addition to the above description, the following experimental partwith the appended photographs will allow a better understanding of thepresent invention. The examples are given purely by way of illustrationwithout wishing to limit the invention.

Experimental Part

The photographs are taken by electron microscopy with a technique forthe selective labelling of the double bonds present in the polymers. Inthese photographs, the character μ means micrometer (μm).

These photographs appear in the following figures:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Morphology of the material obtained in Example 1

FIG. 2: Morphology of the material obtained in Example 2

FIG. 3: Morphology of the material obtained in Example 3

FIG. 4: Morphology of the material obtained in Comparative Example 6(Test 2)

FIG. 5: Enlargement of FIG. 1

FIG. 6: Enlargement of FIG. 2

FIG. 7: Morphology of the material obtained in Example 7, Test 9 ofTable 9

FIG. 8: Morphology of the material obtained in Example 7, Test 4 ofTable 9

FIG. 9: Morphology of the material obtained in Example 9, Test 6 ofTable 12

FIG. 10: Morphology of the material obtained in Example 9, Test 6 ofTable 12 after damaging by impact

FIG. 11: Curve of elongation of the materials in Example 8

Protocol for Studying the Materials by Electron Microscopy

A small sample of a material or of an item which has been shaped from acomposition according to the invention or from a composition not formingpart of the invention (by way of comparison) is removed.

A section with a thickness of between 40 and 60 nanometers is cut fromthis sample using an ultramicrotome. Depending on the stiffness of thesample and in order to obtain a quality section, it may prove necessaryto cool the sample to be cut to −100° C.

In the case where the B blocks originate from the polymerization ofdienes, such as, for example, butadiene or isoprene, the monomer unitsof these B blocks comprise double bonds which react with osmiumtetroxide (OsO₄).

The section obtained is exposed for 15 to 30 minutes to OsO₄ vapour.This exposure makes it possible to selectively label the site of thenanodomains composed of poly(diene). The section thus treated isobserved using a transmission electron microscope. The nanodomainscomposed of B blocks appear as dark on a light background.

In the case where the C blocks comprise phenyl radicals, in particularfor the poly(styrenes), the corresponding nanodomains appear as lightgrey with respect to the lighter background, which corresponds todomains which are inert to OsO₄.

Other techniques for the selective labelling of various polymers for thepurpose of examination by electron microscopy are known in theliterature. Thus, reference may be made to the various methods describedon page 108 in the work Polymer Microscopy (L. C. Sawyer and D. T.Grubb, published by Chapman and Hall, London and New York, 1987).

In the case where the B blocks are formed of a completely hydrogenatedpoly(diene), the blocks can no longer be visualized by OsO₄. On theother hand, the phenyl groups of the poly(styrene) which, in some cases,forms the C blocks or the A blocks can be labelled using rutheniumtetroxide.

Thus, according to the labelling techniques used, the three types ofdomains corresponding respectively to the matrix plus the compatible Ablocks, to the B blocks and to the C blocks can appear in electronmicroscopy with different contrasts.

Thus, for example in order to visualize a multiphase structurecomprising a polyamide and a polyolefin, use can be made of a selectivelabelling of the polyamides using phosphotungstic acid.

The commercial products (Elf Atochem) sold under the trade name Kynar®are homopolymers or copolymers based on PVDF:

Kynar® 400 is available in powder form; its melting temperature is 170°C.

Kynar® 710 is a homopolymer available in the form of granules; itsmelting temperature is 170° C. and its viscosity, measured with acapillary rheometer at 230° C. and 100 s⁻¹, is 600–750 Pa·s.

Kynar® 720 is a homopolymer

M.t. 170° C.

V=750–1050 Pa·s under the same conditions as above.

Kynar® 740 is homopolymer

M.t. =170° C.

V=1750–2150 Pa·s, measured as above.

A triblock denoted by PMMA-PB-PS corresponds to a poly(methylmethacrylate-b-butadiene-b-styrene) triblock terpolymer.

EXAMPLE 1

A PMMA-PB-PS (50/15/35) ABC triblock for which the M_(n) of the PMMAsequences is 50,000 g.mol⁻¹, that of the PB sequences is 15,000 and thatof the PS blocks is 35,000 is prepared according to the proceduredisclosed in EP 524,054 or in EP 749,987.

The crude triblock resulting from the anionic synthesis is purified bymeans of a solid-liquid extraction using cyclohexane as selectivesolvent for the poly(styrene)-poly(butadiene) diblock, the triblockbeing virtually insoluble under the reflux conditions of cyclohexane.

A specific amount of the crude triblock is weighed and then placed in aSoxhlet-type extraction cartridge. The extraction is then begunconventionally. At the end of the extraction, the purified triblock iscontained in the cartridge and the poly(styrene)-poly(butadiene) diblockin cyclohexane. The diblock is recovered by evaporation of thecyclohexane.

As regards the purified triblock, the glass transition temperature ofthe PB sequences, mainly of 1,4 structure, is equal to −90° C. Thepredominantly syndiotactic (>70%).PMMA blocks have a Tg of 130° C.

30 parts by weight of this purified ABC triblock are subsequently mixedfor 4 min at 215° C. in a Brabender mixer with 70 parts by weight ofPVDF homopolymer sold under the trade name Kynar 710 with a melt flowindex (MFI) of 20 cm³/10 min, measured according to ISO Standard 1133 at23° C. under a load of 5 kg. The mixture obtained is calendered and thenpressed at 200° C. to give a material in the form of plates with athickness of 1 mm.

The tensile strength (elongation at break), the stiffness, theappearance and the properties of elongation at break are evaluated underthe conditions indicated below:

♦ Tensile Strength (Elongation at Break)

The elongation at break (ε_(b)) the material and that of Kynar® 710alone and of the triblock alone are measured according to ISO Standard R527. At room temperature, the elongation at break ε_(b) of thecomposition is equal to 400–450%, whereas the elongation at break ε_(b)of Kynar® 710 alone, measured under the same operating conditions, isequal to 130% and that of the triblock alone equal to 6%. Whitening isnot observed on passing the yield point of the composition, which is notdamaged: no cavity is formed, the deformed region is transparent.

♦ Stiffness, Thermal Behaviour

The elastic modulus of the mixture (1500 MPa) is greater than that ofKynar® 710 (1200 MPa) from room temperature to 60° C.; on the otherhand, beyond 60° C., PVDF alone, with an elastic modulus of 200 MPa, isstiffer than the mixture according to the invention, the elastic modulusof which is 150 MPa.

♦ Visual Appearance

The plates of PVDF+triblock mixture are transparent, whereas plates madeof Kynar 710 with the same thickness are hazy.

♦ Examination of the Morphology of the Material (see FIG. 1)

A section with a thickness of between 40 and 60 nanometers (nm) is cutfrom a sample of the material using an ultramicrotome. This section isexposed for 15 to 30 min to osmium tetroxide vapour and the section thustreated is subsequently observed using a transmission electronmicroscope at a magnification of 30,000. The photograph of the imageobserved is presented in FIG. 1: the dark-coloured domains with a sizeof less than 0.02 μm are composed of B blocks incompatible with thelight-coloured matrix composed of the PVDF+PMMA blocks mixture. The darkB domains surround, in a discontinuous fashion, lighter microdomainscomposed of PS blocks, the size of which is between 0.05 and 0.07 μm. Itis found that the dispersion of these multiphase PB and PS noduleswithin the matrix is very fine and very homogeneous.

♦ Resistance to Folding

The resistance to folding of the material obtained is evaluated bymanually folding a test specimen of ISO 1/2 type with a thickness of 2mm perpendicularly to its thickness. It is found that the test specimendoes not whiten at the fold, which is not the case for a test specimenwith the same dimensions made of Kynar 710.

♦ Chemical Behaviour

The ABC triblock is soluble at 23° C. in toluene, whereas thecomposition prepared above and placed for 40 days at 23° C. in tolueneonly exhibits a slight swelling (increase of 2% in mass).

EXAMPLE 2

The PMMA —PB PS (50/15/35) ABC triblock of Example 1 is mixed with aPVDF homopolymer sold under the trade name Kynar® 720 (MFI=10 cm³/10min, measured according to ISO Standard 1133 at 230° C. under a load of5 kg) in the following ratios by mass:

-   -   Test 1: Triblock/Kynar® 720 (07/93) mixture    -   Test 2: Triblock/Kynar® 720 (15/85) mixture.    -   Test 3: Triblock/Kynar 720 (22/78) mixture    -   Test 4: Triblock/Kynar® 720 (30/70) mixture.

The mixtures are prepared in a ZKS twin-screw-extruder at 240° C., aresemi-crystalline and their melting temperature is substantially equal tothat of pure PVDF (170° C.). The granules obtained are injected on aMining press at 230° C., either in the form of 2 mm test specimens or inthe form of bars with a thickness of 4 mm, the mechanical properties ofwhich are measured:

♦ Stiffness

The elastic modulus E is measured in three-point bending, according toISO Standard 178-93 at 23° C.

♦ Resistance to Large Deformations

The measurement is carried out on an ISO 1/2 test specimen (2 mmthickness) with an Instrom tensioning device at a rate of 25 mm/min andat a temperature of 23° C. according to ISO Standard R527. Thedeformation of the test specimen is monitored using a laserextensometer. Each test is carried out on at least five different testspecimens. The following are measured for each of them:

Elongation at yield point: ε_(y) Yield point stress: σ_(y) Elongation atbreak: ε_(b) Stress at break: σ_(b)

♦ Impact Strength

The measurement is carried out on an MGV ZWICK REL 1852instrument-controlled Charpy impact device at 23° C., distance betweensupports 60 mm, at different speeds of impacters: 1 and 2 m·s⁻¹ Themeasurement is carried out on unnotched 4.4×9.7×80 mm bars. The quantitymeasured is the energy dissipated by the sample when it is broken,expressed in joules. When the impact does not cause the bar to break,the material is said to be non-brittle (NB).

By way of comparison, the same tests are carried out on samples of Kynar720 (Control 1). All the results are combined in Table 1.

TABLE 1 Impact E Impact E Test No. E (MPa) ε_(y) (%) σ_(y) (MPa) ε_(b)(%) σ_(b) (MPa) (1 m/s) (2 m/s) Control 1 1580 8.5 ± 0.5  48 ± 1 110 ±10 37 ± 2 8.2 ± 0.5 6.5 ± 0.5 Test 1 1460 10 ± 0.5 41 ± 1 280 ± 10 41 ±2 3.6 ± 0.5 x Test 2 1460 11.5 ± 0.5   37 ± 1 260 ± 10 49 ± 2 3.7 ± 0.5x Test 3 1400 11 ± 0.5 35.5 ± 1   235 ± 10 47 ± 2 NB 10.6 ± 0.5  Test 41400 12 ± 0.5 31 ± 1 210 ± 10 45 ± 2 NB NB NB: The sample does not break

The influence of the temperature on the elongation at break eb of thecomposition of Test No. 4 and of PVDF alone are assessed. The resultsare combined in Table 2.

TABLE 2 Test No. ε_(b) at 20° C. (%) ε_(b) at 0° C. (%) ε_(b) at −10° C.(%) Control 1 100 ± 10  22 ± 4 21 ± 5  Test 4 200 ± 10 147 ± 5 68 ± 15

The influence of the ageing on the materials is assessed by annealingsamples at 120° C. for 15 h. The elongation at break at 23° C. beforeand after annealing is measured. The results are combined in Table 3.

TABLE 3 Test No. ε_(b) before annealing (%) ε_(b) after annealing (%)Control 1 110 ± 10  65 ± 10 Test 1 280 ± 10  85 ± 10 Test 2 260 ± 10 110± 10 Test 3 235 ± 10 250 ± 10 Test 4 210 ± 10 230 ± 10

The specific volume (V_(spec)) of the materials 1 to 4 and of thecontrol is measured at 230° C., on the one hand, and at 30° C., on theother hand, and the shrinkage in volume is calculated (specific volumeat 230° C./specific volume at 30° C.*100). The results are combined inTable 4.

TABLE 4 V_(spec) at 230° C. V_(spec) at 30° C. Shrinkage Test No.(cm³/g) (cm³/g) (%) Control 1 0.6764 0.5624 16.8 Test 1 0.6963 0.585816.3 Test 2 0.7085 0.597 15.7 Test 3 0.7463 0.6394 14.3 Test 4 0.76370.6576 13.9

♦ Stability of the Material (Non-exudation of the Triblock)

The variation in mass of lumps with a mass of 20 mg, withdrawn from thetest specimens of Tests 1 to 4, after 1 h at 200° C. under air isdetermined using a Perkin Elmer TGA7 thermogravimetric balance; thevariation is less than 1%.

By way of comparison, the variation in mass of a lump of test specimenwith the same mass, composed of 90 parts by weight of Kynar 720 and of10 parts by weight of butylbenzenesulphonamide, BBSA (plasticizer), ismeasured; its variation is equal to 10%.

♦ Examination of the Morphology of the Material (see FIG. 2)

Examination with a transmission microscope (TEM) at a magnification of30,000 of a section of the composition of Test 1 (which has beensubjected to an identical treatment to that described in Example 1 andwhich only contains 7 parts by weight of triblock) also shows a fine andeven dispersion of PB nodules with a size of less than 0.02 μm withinthe PVDF+PMMA blocks matrix.

The size of the nodules D_(n) is identical to that of the mixture,richer in the same triblock, of Example 1 (see FIG. 1).

The internodule distance D_(i) is greater than that of Example 1 becausethe number of nodules per unit of volume is much lower.

The dark B domains surround, in a more or less continuous fashion,lighter microdomains composed of PS blocks; the size of which is between0.05 and 0.07 μm. It is found that the dispersion of these multiphase PBand PS nodules within the matrix is very fine and very homogeneous. Thecorresponding photograph is presented in FIG. 2.

EXAMPLE 3 See FIG. 3

25 parts by weight of PMMA-PB-PS (50/15/35) ABC triblock of Example 1and 65 parts by weight of Kynar® 720 and 5 parts by weight of a B-Cdiblock are mixed in a ZKS twin-screw extruder at 240° C.; this PB-PS(30/70) diblock is a by-product of the anionic polymerization of the ABCtriblock and is composed of a PB block with an M_(n) of 15,000 g.mol⁻¹and of a PS block with an M_(n) of 35,000. The mixture obtained issemi-crystalline and its melting temperature is substantially equal tothat of pure PVDF (170° C.). The granules obtained are injected on aMining press at 230° C., either in the form of 2 mm test specimens or inthe form of bars with a thickness of 4 mm, the mechanical properties andthe chemical behaviour of which are measured. The results obtained aresubstantially identical to those of the material of Test No. 4 ofExample 2.

A section with a thickness of between 40 and 60 nm is cut from a sampleof the material using an ultramicrotome. This section is exposed for 15to 30 min to osmium tetroxide vapour and the section thus treated issubsequently observed with a transmission electron microscope at amagnification of 50,000. The photograph of the image observed ispresented in FIG. 3: the dark-coloured nodules with a size of less than0.02 μm are composed of B blocks which are incompatible with thelight-coloured matrix composed of the PVDF+PMMA blocks mixture. Some ofthese B blocks are present in an external peripheral region of eachnodule and surround, in a discontinuous fashion, the internal region ofthe nodule, which emerges in grey. Other B blocks are situated withinthis internal region. The reasonable hypothesis may be put forward thatthe latter nanodomains of B blocks originate from thepoly(butadiene-b-styrene) B-C diblocks, by comparison with themorphology obtained in Example 1, where the triblock does not compriseB-C diblocks. This is because the B-C diblocks have more affinity forthe C blocks of the internal region of the nodules than the A-B-Ctriblocks, which are drawn towards the matrix by the A blocks, which arecompatible with the latter.

A dispersion of the nodules within the matrix is found which is fully asfine and homogeneous as for the compositions according to the inventionnot comprising B-C diblock.

EXAMPLE 4

A PMMA-PB-PS (58/11/31) ABC triblock for which the M_(n) of the PMMAsequences is 58,000 g.mol⁻¹ that of the PB sequences is 11,000 and thatof the PS blocks is 31,000 prepared according to the procedure disclosedin EP 524,054 or in EP 749,987.

This triblock is mixed with Kynar 720 and a C-B-C triblock, i.e.PS-PB-PS (15/70/15) with an M_(n) of 100,000 g.mol⁻¹ under the operatingconditions of Example 2.

The notched Charpy impact strength of the materials obtained is measuredat 23, 0 and −10° C. with an impact speed of 1 m.s⁻¹ as indicated inExample 2.

The proportions by mass of the constituents (PVDF, A-B-C and C-B-C) ofeach of the materials tested and the results of impact strength tests at23, at 0 and at −10° C. are combined in Table 5.

TABLE 5 Impact strength B means Broken mCBC × 100 mB × 100 NB meansNon-Broken Test No. mPVDF mABC mCBC m(PVDF + ABC) m(ABC + CBC) 23° C. 0°C. −10° C. Control 2 100 0 0 0 0 B B B Test 5 75 25 0 0 2.75 NB B B Test6 75 18.75 6.25 6.7 6.2 NB NB NB Control 3 75 13.25 11.75 15 9 NB NB BTest 7 85 7 8 8.7 6.2 NB B B

EXAMPLE 5

25 parts by weight of the triblock of Example 2 are mixed in a Haaketwin-screw extruder at 190° C. with 75 parts by weight ofsemi-crystalline PVC sold under the trade name GB 1150. Strips with athickness of 4 mm and a width of 35 mm are extruded using a slot dieplaced at the extruder outlet, from which strips are cut out testspecimens, in order to evaluate the softening temperature under stress(Vicat temperature) according to ISO Standard 306-94 on 5 samples, andto calculate the corresponding standard deviation, as well as the impactstrength according to ISO Standard 179-93.

By way of comparison, the Vicat temperature and the impact strength ofthe PVC resin alone (Control 4) are measured under the same operatingconditions. The results are combined in Table 6.

TABLE 6 T_(vicat) under 50N Standard deviation Impact S at 23° C. TestNo. (° C.) (° C.) (kJ/m²) Control 4 79.9 0.4 4 Test 8 86.1 0.5 5

COMPARATIVE EXAMPLE 6 See FIG. 4

The following tests show the major disadvantage of the presence of aside-product homopolymer usual in the synthesis of a diblock.

The poly(butadiene)-poly(methyl methacrylate), PB-PMMA, diblock withoutsignificant presence of homopolymer is obtained by the same syntheticroute as the PS-PB-PMMA triblock. It has an M_(n) of 100,000 g.mol⁻¹,and is composed of 50% of PMMA and of 50% of PB by moles by number. ThePB homopolymer was separated by a solid-liquid extraction withcyclohexane as solvent.

The material consisting of 70% of PVDF, of 25% of the PB-PMMA diblockand 5% of PB homopolymer is obtained in the same way as in the precedingexamples.

The elongation at break of the materials which appear in Table 7 ismeasured with the following results:

TABLE 7 Elongation at Comparative break according to Test No.Compositions, % by weight the ISO test 1 100% PVDF    50% 2 75% PVDF +25% PB-PMMA >200% diblock 3 70% PVDF + 30% PB-PMMA >200% diblock 4 70%PVDF + 25% PB-PMMA    10% diblock + 5% PB homopolymer

Test No. 4 shows the loss in ductility caused by the presence of 5% ofpoly(butadiene).

The morphology of Test No. 2 appears in FIG. 4. Nodules uniformly filledwith a black or dark colour are observed. This colour corresponds to thelabelling of the poly(butadiene) blocks with osmium tetroxide.

These PB blocks thus constitute the interior of the nodules.

EXAMPLE 7 See FIGS. 7 and 8

Various PMMA-PB-PS triblocks were prepared according to, the proceduredisclosed in EP 524,054 or EP 749,987. Their characteristics are listedin Table 8.

TABLE 8 % PB % PMMA by % PS Total % Product by weight weight by weightby weight M_(n) PI ABC1 36 28 35 99 80,400 1.7 ABC2 31 22 46 99 100,0001.9 ABC3 34 31 35 100 113,300 1.8 ABC4 50 29 21 100 90,000 2.2 ABC5 3336 31 100 80,000 2.0

The molar mass M_(n) of each triblock is measured by steric exclusionchromatography and the values are expressed in g.mol⁻¹ as polystyreneequivalent. The polydispersity index PI is defined by the ratio of themolecular mass by weight to the molecular mass by number, i.e.M_(w)/M_(n).

The fractions by mass of PMMA, PB and PS are determined by NMR. Theseproducts comprise a B-C (PS-PB) diblock fraction and a C (PS)homopolymer fraction. B-C and C are synthetic intermediates and theynever represent more than 25% of the final product.

In all cases, the glass transition temperature of the PB block is −90°C. The PMMA sequences are syndiotactic to more than 70%. The PMMA blockhas a Tg of 135° C.

Preparation Process

One of these five. ABC triblocks above is mixed in a ZKS twin-screwextruder at between 230° C. and 240° C. with a commercial PVDF from thecompany Elf Atochem. The compositions of the various mixtures preparedare given in Table 9 below.

The granules obtained are injected on a Mining press in the form of80×10×4 mm bars, the mechanical properties of which are measured, inparticular the impact strength by the notched. Charpy impact test atvarious temperatures according to ISO Standard 179/93-1eA.

TABLE 9 Material Mean impact strength (kJ/m²) Composition 23° C. 0° C.−10° C. −20° C. −30° C. Control 1 Kynar 740 10.6B 10B  9.6B  9B  6.6BTest 1 Kynar 740/ABC1 90/10 31.5 15B 15B 12.6B 11.6B Test 2 Kynar740/ABC1 85/15 47 26 16B 13.6B 12.4B Test 3 Kynar 740/ABC1 80/20 55 5552 22 16B Test 4 Kynar 740/ABC1 75/25 55 55 52 49 18B Test 5 Kynar740/ABC2 85/15 32 15B 15B 14B 12B Test 6 Kynar 740/ABC2 75/25 36 32 1917B 15B Test 7 Kynar 740/ABC3 85/15 51 18 15B 14B 11B Test 8 Kynar740/ABC3 75/25 54 53 42 21 15B Test 9 Kynar 740/ABC4 80/20 45 45 40 1713B Test 10 Kynar 740/ABC5 85/15 37 37 33 16 12B Test 11 Kynar 740/ABC580/20 37 35 33 23 12B Test 12 Kynar 740/ABC5 75/25 39 38 37 32 22Control 2 Kynar 400 30 17 15B 15B 12B Test 13 Kynar 400/ABC1 80/20 98 9585 80 60

The values indicated with a “B” correspond to the samples which exhibitbrittle failure. The other samples exhibit ductile failure.

Comparison of Tests 1 to 13 with Control 1:

it is not able that strengthening with regard to impacts is obtainedwith all the ABC triblocks tested.

Comparison of Tests 1, 2, 3 and 4, comparison of Tests 5 and 6,comparison of Tests 7 and 8 and comparison of Tests 10, 11 and 12:

It is observed that the improvement increases as the level of triblockincreases in the range 10 to 25%. This is reflected by a shift towardslow temperature. This property is essential in numerous applications.

Modulus/impact compromise:

The improvement in the impact is usually made at the expense of themodulus.

It is noteworthy that this improvement in the impact properties of thePVDF is obtained, on the one hand, without significant lowering (<10%)of the flexural modulus of the PVDF and, on the other hand, withoutlowering of the melting temperature of the material (<3° C.).

It should be noted that for the first time to the knowledge of theApplicant Company, a material composed of more than 80% of PVDF (Test13), having a modulus substantially equal to PVDF and a meltingtemperature substantially equal to PVDF, exhibits ductile behaviour in anotched Charpy impact test at −30° C.

Morphology:

All these materials have a specific morphology.

FIG. 8 corresponds to Test 4. It is found that, in the nodules, PBblocks appear visualized within an internal region predominantlycomposed of C blocks and surrounded by a continuous external peripheralregion forming a kind of black ring comprising the PB blocks of thetriblocks. Examination of the morphologies between this example andExample 1, in which the triblock comprises no diblock, makes it possibleto maintain that the PB blocks situated within the nodules can beattributed to the PS-PB diblocks.

FIG. 7 corresponds to Test 9. It shows a morphology analogous to that ofTest 4 at a greater magnification.

The evenness of the domains can be detrimentally affected to a slightextent during the conversion (effect of the shearing).

Comment on the conversion (ease of producing these materials):

It has been found, in an entirely surprising way, that the properties ofthe materials obtained are not dependent on the state in which theproducts are provided before mixing. Thus, by mixing PVDF granules and atriblock powder, the same results are obtained as =by mixing a PVDFpowder and a triblock powder or a PVDF powder and triblock granules orPVDF granules and triblock granules.

EXAMPLE 8

An ABC triblock is mixed in a ZKS twin-screw extruder at between 230° C.and 240° C. with a commercial PVDF from the company Elf Atochem. Thecompositions of the various mixtures prepared are given in Table 8.

The granules obtained are injected on a Mining press in the form of ISO1/2 test specimens (thickness of 2 mm), the tensile behaviour of whichis measured. The deformation of the test specimen is monitored using alaser extensometer, the tensioning rate is 25 mm/min and the temperatureis controlled at 23° C. The curves of stress as a function of elongationare represented in FIG. 11 and the main results are taken up in Table10.

TABLE 20 Material Tensile behaviour Composition ε_(b) (%) CommentControl 1 Kynar 740 60 Very marked necking Test 1 Kynar 740/ 85/15 70Very slight necking ABC4 Test 2 Kynar 740/ 80/20 130 No necking, nodetect- ABC4 able yield point, homogeneous defor- mation Test 3 Kynar740/ 70/30 200 No necking, yield ABC4 point scarcely detect- able,homogeneous deformation

Comment:

The addition of ABC triblock to the PVDF completely alters its tensilebehaviour. A material which does not neck and which deformshomogeneously is obtained. This property is essential in numerousapplications where the appearance of damage (necking) beyond 10%elongation is harmful.

It is surprising that this alteration in the tensile behaviour isobtained without significant decrease in the modulus of the material.

Preparation of films:

Films were processed on a microextruder of Randcastle RCP0500 trade markstarting with ABC+PVDF granules. The temperature profile was set at 210°C. in the first two heating regions and at 185° C. at the die. Films forwhich the thickness could be controlled between 10 μm and 400 μm wereobtained.

Tensile tests were carried out on these films. The PVDF film (Kynar 740)necks, whereas the films obtained by mixing Kynar 740 with 15% of ABC1and the films obtained by mixing Kynar 740 with 15% of ABC4 do notexhibit necking and deform homogeneously. This property is important inapplications in films or in bubble form in extrusion blow-moulding.

It also makes it possible to prepare products for preparing coextrusionbinders.

Measurements of Permeability to Fuels and to Solvents

Measurements of permeability to fuels, to methanol and, to toluene werecarried out starting with the films prepared above. It was found thatthe ABC+PVDF materials retain excellent barrier properties.

The combination of these excellent barrier properties, of the specifictensile behaviour (absence of necking) and of the excellent impactproperties make ABC+PVDF materials perfectly suited to the preparationof (mono- or multilayer) pipes or of extruded or moulded components usedfor the transportation or storage of petrols, organic solvents oraggressive fluids.

EXAMPLE 9 PVC+PMMA-PB-PS Triblock

The addition of ABC triblock to PVC facilitates the conversion of thelatter. This can be demonstrated by measuring the time necessary toobtain a homogeneous molten sheet on a counter-rotating twin-rollcalender (known as melting time). Furthermore, the addition of ABCtriblock results in a material for which the impact properties (measuredaccording to ISO Standard 179/93-1EA) and the Vicat point (measuredaccording to ISO Standard 306/94-B50) are improved. This result isentirely surprising because:

-   -   conventional impact additives for PVC, such as core-shells (MBS)        and acrylic core-shells result in a decrease in the Vicat point,    -   conventional “heat” additives for PVC make it possible to        improve the Vicat point but result in a lessening of the impact        properties.

Another surprising point is that the improvement in all these propertiesis not made at the expense of the transparency of the material.

Various PMMA-PB-PS triblocks were prepared according to the proceduredisclosed in EP 524,054 or in EP 749,987. Their characteristics arelisted in Table 11.

TABLE 11 % PMMA % PB % PS Product by weight by weight by weight M_(n) PIABC1 36 28 35 80,400 1.7 ABC4 50 29 21 90,000 2.2

Effect on the Conversion

Several grades of commercial PVC from Elf Atochem were used, the K valueof which varies between 57 and 70. These products were preformulatedwith 2 parts of heat stabilizer, 1.9 parts of external lubricants and1.5 parts of processing aid. Various dry mixings were carried out withthe same composition by mass of 75% of preformulated PVC and of 25% ofABC triblock.

One of its PVC grades (K value of 67) was formulated with only 0.6 partof lubricant and 2 parts of heat stabilizer (without processing aid),which is Control No. 4. Two mixtures were prepared with 15% and with 25%of ABC triblock. The results obtained are given in Table 12.

TABLE 12 Temperature of the rolls Sheeting Reference Product (° C.) time(min) Control 1 PVC, K value of 57 190 12 Test 1 Control 1/ABC1 75/25190 5 Test 2 Control 1/ABC4 75/25 190 9 Control 2 PVC, K value of 67 20029 Test 3 Control 2/ABC1 75/25 200 4 Test 4 Control 2/ABC4 75/25 200 12Control 3 PVC, K value of 70 215 7 Test 5 Control 3/ABC1 75/25 215 4Test 6 Control 3/ABC4 75/25 215 6 Control 4 PVC, K value of 67 190 >30Test 7 Control 4/ABC4 85/15 190 6 Test 8 Control 4/ABC4 75/25 190 5

Comments

It is found that the addition of triblock significantly reduces thesheeting time of the product. This constitutes a major advantage of theformulation according to the invention. Other products have the sameeffect but, to our knowledge, none exhibits the combination ofproperties of these formulations (processing, Vicat, impact).

The addition of ABC triblock to Control No. 4 makes it possible toconvert this product at 190° C., whereas it cannot be converted alone atthis temperature.

Joint Improvement in the Impact Properties and in the Vicat Point

Various sheets of PVC+ABC mixtures are prepared on a twin-roll calenderwith the same procedure as described above. The sheets obtained arepress-moulded in the form of plates with a thickness of 4 mm at 195° C.for 8 min.

88×10×4 mm bars are cut out from these plates in order to carry outnotched Charpy impact measurements at 23° C. according to ISO Standard179/93-1EA. The Vicat point measurements are carried out on these platesaccording to ISO Standard 306/94-B50. The results obtained are given inTable 13.

TABLE 13 Impact strength Vicat at 23° C. temperature, Reference Product(kJ/m²) 50N (° C.) Control 2 Pvc, K value of 57 5.5 B 79.5 Test 9Control 2/ABC4 85/15 20 81.4 Test 10 Control 2/ABC4 80/20 30 82.3 Test 6Control 2/ABC4 75/25 64 82.9 Test 11 Control 2/ABC4 60/40 25 83.6

The values indicated with a “B” correspond to the samples which exhibitbrittle failure. The other samples exhibit ductile failure.

Structure

All these materials have a specific structure as described below.

A transmission electron microscopy exposure carried out on a samplewithdrawn from a bar corresponding to Test 6 is appended (FIG. 9).

We again demonstrate that the structure is an intrinsic characteristicof the materials according to the present invention.

The evenness of the domains can be detrimentally affected to a slightextent during the conversion (effect of the shearing).

A transmission electron microscopy exposure was carried out on a damagedbar (recovered after the notched Charpy impact test). The regionobserved corresponds to the region where the material has deformed in aductile way (FIG. 10). It is found on this exposure that, surprisingly,the deformation is extremely homogeneous. Extremely numerous microholeshave been created within the domains constituted by the B and C blocksof the ABC triblock. The creation of these holes is a key factor indissipating energy and thus strengthening the material with respect toimpact.

EXAMPLE 10 Chlorinated poly(vinyl chloride) (CPVC)+PS-PB-PMMA Triblock

The addition of ABC triblock to CPVC facilitates the conversion of thelatter. This can be demonstrated by measuring the time necessary toobtain a homogeneous molten sheet on a counter-rotating twin-rollcalender (known as melting time). Furthermore, the addition of ABCtriblock results in a material with improved impact properties (measuredaccording to ISO Standard 179/93-1EA). According to the content ofchlorine in the CPVC, this improvement in impact properties takes placein conjunction with an increase or a decrease in the Vicat point(measured according to ISO Standard 306/94-B50).

Another surprising point is that the triblocks make it possible toobtain values of impact strength which are unequalled, to the knowledgeof the Applicant Company.

Another surprising point is that the improvement in all these propertiesdoes not take place at the expense of the transparency of the material.

Several grades of CPVC were used, the K value of which varies between 57and 67 and the chlorine content of which varies between 62% and 69%.These products were preformulated with 2 parts by weight of heatstabilizer, 1.9 parts of external lubricants and 1.5 parts of processingaid. Various dry mixings were carried out with 15% of ABC triblock. Theresults obtained are given in Table 14.

TABLE 14 Temperature of the rolls Sheeting Reference Product (° C.) time(min) Control 1 CPVC, K value of 57, 65% Cl 200 17 Test 1 Control 1/ABC185/15 200 6 Test 2 Control 1/ABC4 85/15 200 6 Test 3 Control 1/ABC685/15 200 7 Control 2 CPVC, K value of 67, 65% Cl 215 20 Test 4 Control2/ABC1 85/15 215 3 Test 5 Control 2/ABC4 85/15 215 5 Test 6 Control2/ABC6 85/15 215 8

Various sheets of CPVC+ABC mixtures are prepared on a twin-roll calenderwith the same procedure as described above. The sheets obtained arepress-moulded in the form of plates with a thickness of 4 mm at 1950° C.for 8 min.

80×10×4 mm bars are cut out from these plates in order to carry outnotched Charpy impact measurements at 23° C. according to ISO Standard179/93-1EA. The Vicat point measurements are carried out on these platesaccording to ISO Standard 306/94-B50. The results obtained are given inTable 15;

TABLE 15 Impact strength Vicat at 23° C. temperature, Reference Product(kJ/m²) 50N (° C.) Control 1 CPVC, K value of 57, 65% Cl 2.7 B 102.9Test 7 Control 1/ABC1 75/25 48.5 102 Test 8 Control 1/ABC6 75/25 8.7104.2 Control 2 CPVC, K value of 67, 65% Cl 3.1 B 106.4 Test 4 Control2/ABC1 85/15 9.3 103.4 Test 5 Control 2/ABC4 85/15 17.5 104.6 Control 3CPVC, K value of 57, 62% Cl 3.2 B 90.3 Test 9 Control 3/ABC1 75/25 63.391.3 Test 10 Control 3/ABC6 75/25 8.5 94.4 Control 4 CPVC, K value of57, 67% Cl 1.9 B 113.3 Test 11 Control 4/ABC1 75/25 23.6 107.1 Test 12Control 4/ABC6 75/25 15.3 111.5 Control 5 CPVC, K value of 57, 69% Cl1.8 B 124.5 Test 13 Control 5/ABC1 75/25 13.3 113.6 Test 14 Control5/ABC6 75/25 10.4 117.6

The values indicated with a “B” correspond to the samples which exhibitbrittle failure. The other samples exhibit ductile failure.

CONCLUSIONS

The ABC triblocks, added to CPVCs with a chlorine content of less than65%, make it possible to obtain a material which can be more easilyconverted, with a higher Vicat point and with exceptional impactproperties.

The ABC triblocks, added to the CPVCs with a chlorine content of greaterthan 65%, make it possible to obtain a material which can be more easilyconverted and with excellent impact properties.

1. A composition consisting essentially of: a thermoplastic fluorinatedresin X1 or several compatible thermoplastic resins X1 to Xn, wherein atleast one of X1 to Xn is fluorinated, and at least one block(sequential) copolymer, n being an integer equal to or greater than 1,wherein: the block copolymer comprises at least three blocks A, B, andC, wherein each block is either a homopolymer or a copolymer obtainedfrom two or more monomers, the A block is connected to the B block andthe B block is connected to the C block by means of a covalent bond orof an intermediate molecule connected to one of these blocks via acovalent bond and to another block via another covalent bond, the Ablock is compatible with the thermoplastic resin or resins X1 to Xn, theB block is incompatible with the thermoplastic resin or resins X1 to Xnand incompatible with the A block, the C block is incompatible with thethermoplastic resin or resins X1 to Xn, the A block and the B block;said composition comprising, by weight, at least 50% of thethermoplastic fluorinated resin(s), based on the total weight offluorinated resin(s) and the block copolymer being at least one blockcopolymer with a number-average molecular mass (Mn) of greater than orequal to 20,000 g.mol−1 composed of: 20 to 93 parts by weight of Asequences, 5 to 50 parts by weight of B sequences, and 2 to 50 parts byweight of C sequences; and wherein said thermoplastic fluorinatedresin(s) comprises poly(vinylidene difluoride) (PVDF) and said blockcopolymer is a poly(methyl methacrylate)-poly(butadiene)-poly(styrene)triblock copolymer.